Multiple access is one of core technologies at a physical layer for wireless communication, through which a radio base station can distinguish and serve a plurality of terminal users and reduce multiple-access interference. A simple orthogonal multiple access scheme is used in most of existing wireless communications systems. Because a quantity of access users who can be accommodated by an orthogonal multiple access technology is in direct proportion to a quantity of orthogonal resources, and the quantity of orthogonal resources is confined due to an orthogonality requirement, future 5G (Fifth Generation) service requirements such as wide-area continuous coverage, a high-capacity hotspot, massive connections, and low-delay access cannot be satisfied. Therefore, non-orthogonal multiple access gradually becomes a researching focus of currently attractive 5G multiple access.
A sparse code multiple access (Sparse Code Multiple Access, SCMA) technology is a typical non-orthogonal multiple access and transmission technology. Such technologies can effectively increase a network capacity, including a quantity of users who can access the system, spectral efficiency, and the like.
In the SCMA technology, an SCMA codebook is used to modulate to-be-transmitted information bits, to implement sparse spreading. In the prior art, a series of constellations may be generated based on a multidimensional mother modulation constellation, and then the constellations are used as codebooks. However, when a modulation symbol generated by using the existing SCMA technology is demodulated, a very complex solution is needed.